HUMAN IMMUNE CELL MATURATION DURING ONTOGENY AND INFECTION This program represents a new and promising collaboration between five investigators at the University of California, San Francisco and Stanford University, all of whom work on complementary aspects on human immunology. The five problems addressed in the individual units investigate regulatory mechanisms influencing human immune cell maturation during ontogeny and infection. Each sit describes a collaboration with at least one other investigator in the program and reflects the shared interests and expertise of the investigators involved. All of our laboratories are committed to studying the human immune response. This commitment arises broth from an interest in human disease and the fact that several of use study systems that are markedly different in humans than in the prevailing mouse model systems. Together the proposed projects define unique aspects of the human immune response in comparison to murine and non-human primate systems, analyze the role of signaling and membrane traffic in regulation of human lymphoid development and study the effects of infectious diseases in humans on lymphoid maturation and function.